Recording medium, method of manufacturing recording medium and recording apparatus

ABSTRACT

A recording medium includes a substrate, and a recording layer formed on the substrate having (a) a recording track band, and (b) recording cells regularly arrayed in the recording track band to form a plurality rows of sub-tracks. The recording cells included in each sub-track are formed apart from each other at a pitch P in the track direction. Nearest neighboring two recording cells, each positioned on adjacent two sub-tracks in the track band, are formed apart from each other at a pitch P/n in the track direction, where 2≦n≦5.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2001-082436, filed Mar.22, 2001, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a recording medium capable ofhigh-density recording, a method of manufacturing a recording medium,and a recording apparatus.

[0004] 2. Description of the Related Art

[0005] Information handled by users is being markedly increased bydrastic improvement in functions of information apparatuses such aspersonal computers. Under the circumstances, demands for an informationrecording-reproducing apparatus with a drastically improved recordingdensity are being made higher and higher. In order to improve therecording density, it is necessary to miniaturize the size of a singlerecording cell or a recording mark, which constitutes the writing unitof recording on the recording medium. However, the miniaturization ofthe recording cell or the recording mark faces a series difficulty inthe conventional recording medium.

[0006] For example, in a magnetic recording medium such as a hard disk,a polycrystalline material having a wide grain size distribution is usedfor forming the recording layer. However, the recording is renderedunstable in the recording layer formed of small polycrystalline grainsbecause of thermal fluctuations of the crystal. Therefore, if therecording cell is small, recording is rendered unstable and noisegeneration is increased, though a problem is not generated in the casewhere the recording cell is large. The unstable recording and theincreased noise generation are brought about because, if the recordingcell is small, the number of crystals contained in the recording cell isrendered small and interaction among the recording cells is renderedrelatively large.

[0007] This is also the case with an optical recording medium using aphase change material. Specifically, recording is rendered unstable andmedium noise is increased in a recording density not lower than severalhundred gigabits per square inch, in which the recording mark size issubstantially equal to the grain size of the phase change material.

[0008] In order to avoid the difficulties pointed out above, proposed inthe field of the magnetic recording is a patterned media, in which arecording material is divided in advance by a non-recording material soas to carry out a recording-reproducing by using a single recordingmaterial particle as a single recording cell, as disclosed in, forexample, U.S. Pat. Nos. 5,587,223, 5,956,216 and 6,162,532.

[0009] However, a lithography technique is used in the conventionalmethod of forming the structure in which the recording materialparticles are isolated. It is certainly possible for optical lithographyto cope with the requirement of a high recording density in terms ofthroughput because single step exposure can be employed. However, theoptical lithography is hard to process recording cells sufficientlysmall in size. Electron beam lithography or a focused ion beam permitfine processing of about 10 nm. However, it is difficult to put thesetechniques into practical use in view of the processing cost and theprocessing speed.

[0010] Japanese Patent Application Laid-open Publication No. 10-320772discloses a method of manufacturing a magnetic recording medium havingisolated magnetic fine particles formed on a substrate by lithographytechnology using a mask of fine particles having a size of severalnanometers to several micrometers, which are two-dimensionally arrayedon a substrate. The method provides a cheap manufacturing method of apatterned media.

[0011] A method of ordering fine particles two-dimensionally on asubstrate is proposed in, for example, S. Hung et al., Jpn. J. Appl.Phys., 38 (1999) pp. L473-L476. It is proposed that a substrate iscoated with fine particles covered with long-chain alkyl groups so as topermit a relatively uniform single particle layer to be formed to covera large area by utilizing autoagglutination of the fine particles duringdrying.

[0012] Also known is a method of forming a regular array structure on asubstrate by utilizing a self-ordering phase separation structure formedby a block copolymer, as reported in, for example, M. Park et al.,Science 276 (1997) 1401. It is reported that, in a block copolymer suchas polystyrene-block-polybutadiene or polystyrene-block-polyisoprene, itis possible to leave the polystyrene block alone by ozone treatment, andto form a structure of holes or a line-and-space on the substrate byusing the left polystyrene block as an etching mask.

[0013] In a film-forming method in which self-ordering particles such asfine particles or block copolymer are arrayed two-dimensionally on asubstrate, it is possible to obtain a structure in which theself-ordering particles are microscopically arrayed to form a lattice.However, many defects and crystal boundaries are present macroscopicallyso as to form a lattice directed at random, resulting in failure toachieve practical recording/reproducing.

[0014] Also, in the conventional magnetic recording medium having auniform structure, signals are written at a predetermined interval.Therefore, even if a write error takes place, the recording cells arerendered defective only partly, making it possible to read out thewritten information at the same time interval in the entire system. Onthe other hand, when it comes to the patterned media in which therecording cells are formed in advance, it is necessary to perform theprocessing such that the distances between the adjacent recording cellsare rendered constant. Even if it is possible to manufacture a patternedmedia utilizing the self-ordering particles, it is necessary to form asingle regular array free from an internal disturbance or defect in theentire region. However, where ordering processes have taken place fromtwo different sites within the same region, a regular triangular latticeis formed inside each of the self-ordering array. However, the latticeposition of one of these two self-ordering arrays does not match withthe lattice position of the other self-ordering array. As a result,discontinuity of the lattices is generated in the connecting area of theadjacent self-ordering arrays. Since the read interval of the recordingcells differs in the discontinuous portion of the lattices, reproductionof information is rendered difficult. As described above, a region wherethe array is disturbed is generated as a defect inherent in therecording medium utilizing the self-ordering array, with the result thatit is necessary to establish a method of avoiding read errors for usingthe particular recording medium.

[0015] It should also be noted that the track density is increased withincrease in the recording density so as to make it very difficult towrite servo marks for tracking. A method of achieving a high trackdensity is proposed in, for example, Japanese Patent ApplicationLaid-open Publication No. 6-111502. It is proposed that a servo patternfor tracking is formed in advance in the disk as a physical irregularpattern. In this method, formed is a track close to a true circle,making it possible to increase the track density, compared with theconventional HDD. However, when it comes to a high recording densitysuch as 100-giga(G) bpsi to 1-tera(T) bpsi, it is difficult to form theservo pattern by cheap lithography. Further, in the recording mediumutilizing the self-ordering, a regular array structure inherent in theself-ordering particles is formed in the track. It follows that it isimpossible for the conventional tracking method to access the recordingcells formed of self-ordering particles.

[0016] As described above, patterned media are an effective means forrealizing a high recording density of the order of Tbpsi. However, amethod that permits the manufacture of a pattern with a low cost andwith a high throughput has not yet been established. Also, the methodusing the self-ordering of a material permits the manufacture of apattern with a low cost and with a high throughput. However, a mediumhaving an entirely arrayed structure to permit access to recorded datahas not yet been obtained.

BRIEF SUMMARY OF THE INVENTION

[0017] An object of the present invention is to provide a recordingmedium in which a pattern of the recording cells is highly arrayed,which can be manufactured easily, and which permits reading informationwith a high speed, a method of manufacturing the particular recordingmedium, and a recording apparatus.

[0018] According to one aspect of the present invention, there isprovided a recording medium, comprising: a substrate; and a recordinglayer formed on the substrate comprising (a) a recording track band, and(b) recording cells regularly arrayed in the recording track band toform a plurality rows of sub-tracks, wherein the recording cellsincluded in each sub-track are formed apart from each other at a pitch Pin the track direction, and wherein nearest neighboring two recordingcells, each positioned on adjacent two sub-tracks in the track band, areformed apart from each other at a pitch P/n in the track direction,where 2≦n≦5.

[0019] According to another aspect of the present invention, there isprovided a method of manufacturing a recording medium, comprising:forming on a substrate a continuous or intermittent groove region, or aband region containing a specified chemical component, which correspondsto a recording track band; forming a two-dimensional regular arraystructure of self-ordering molecules or fine particles in the grooveregion or the band region; and forming recording cells corresponding tothe regular array structure.

[0020] In this method, optical lithography, electron beam lithography ornano-imprinting lithography is employed for forming the groove region orthe band region.

[0021] According to another aspect of the present invention, there isprovided a recording apparatus, comprising: a recording mediumcomprising a substrate and a recording layer formed on the substratecomprising (a) a recording track band and (b) recording cells regularlyarrayed in the recording track band to form a plurality rows ofsub-tracks, wherein the recording cells included in each sub-track areformed apart from each other at a pitch P in the track direction, andwherein nearest neighboring two recording cells, each positioned onadjacent two sub-tracks in the track band, are formed apart from eachother at a pitch P/n in the track direction, where 2≦n≦5; a write head;and a read head.

[0022] According to another aspect of the present invention, there isprovided a recording apparatus writing to and reading from a recordingmedium comprising a substrate and a recording layer formed on thesubstrate comprising (a) a recording track band and (b) recording cellsregularly arrayed in the recording track band to form a plurality rowsof sub-tracks, wherein the recording cells included in each sub-trackare formed apart from each other at a pitch P in the track direction,and wherein nearest neighboring two recording cells, each positioned onadjacent two sub-tracks in the track band, are formed apart from eachother at a pitch P/n in the track direction, where 2≦n≦5, comprising; awrite head; a read head; and a controller controlling write timingsignals supplied to the write head in accordance with signals generatedfrom the read head.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0023]FIG. 1 is a plan view showing a recording medium according to oneembodiment of the present invention;

[0024]FIGS. 2A to 2D are cross-sectional views showing a method ofmanufacturing a magnetic recording medium for Example 1 of the presentinvention;

[0025]FIG. 3 is a plan view showing the magnetic recording medium forExample 1 of the present invention;

[0026]FIGS. 4A to 4D are cross-sectional views showing a method ofmanufacturing a magnetic recording medium for Example 5 of the presentinvention;

[0027]FIG. 5 is a plan view showing the magnetic recording medium forExample 5 of the present invention;

[0028]FIGS. 6A to 6C are cross-sectional views showing a method ofmanufacturing a master disk used for the manufacture of a magneticrecording medium for Example 8 of the present invention;

[0029]FIGS. 7A to 7D are cross-sectional views showing a method ofmanufacturing the magnetic recording medium for Example 8 of the presentinvention;

[0030]FIGS. 8A to 8C are cross-sectional views showing a method ofmanufacturing a magnetic recording medium for Example 9 of the presentinvention;

[0031]FIGS. 9A to 9D are cross-sectional views showing a method ofmanufacturing a magnetic recording medium for Example 10 of the presentinvention;

[0032]FIG. 10 is a plan view showing the magnetic recording medium forExample 10 of the present invention;

[0033]FIG. 11 is a perspective view showing the internal construction ofa magnetic disk apparatus for Example 11 of the present invention;

[0034]FIG. 12 is a cross-sectional view showing the magnetic disk andthe head slider for Example 11 of the present invention;

[0035]FIG. 13 schematically shows the planar construction of the headslider for Example 11 of the present invention;

[0036]FIG. 14 shows the arrangement of the reading head relative to therecording track band for Example 11 of the present invention;

[0037]FIGS. 15A to 15C show the tracking method for Example 11 of thepresent invention;

[0038]FIG. 16 shows how to avoid writing in a defective region inExample 11 of the present invention;

[0039]FIG. 17 is a block diagram showing a controller for controllingthe read head, the write head, and the voice coil motor in Example 11 ofthe present invention;

[0040]FIG. 18 is a cross-sectional view showing the magnetic disk andthe head slider for Example 12 of the present invention;

[0041]FIG. 19 schematically shows the planar construction of the headslider for Example 12 of the present invention;

[0042]FIGS. 20A and 20B show the arrangements of the read head, thewrite head and the tracking head relative to the recording track band inExample 12 of the present invention;

[0043]FIGS. 21A to 21D are cross-sectional views showing a method ofmanufacturing a phase change optical recording medium for Example 13 ofthe present invention;

[0044]FIG. 22 is a plan view of the phase change optical recordingmedium for Example 13 of the present invention;

[0045]FIG. 23 is a cross-sectional view showing the phase change opticaldisk and the head slider for Example 14 of the present invention;

[0046]FIG. 24 schematically shows the planar construction of the headslider for Example 14 of the present invention;

[0047]FIG. 25 is a cross-sectional view showing the magnetic disk andthe head slider for Example 15 of the present invention;

[0048]FIG. 26 schematically shows the planar construction of the headslider for Example 15 of the present invention;

[0049]FIG. 27 shows the arrangement of the read head, the write head andthe tracking head relative to the recording track band for Example 15 ofthe present invention;

[0050]FIG. 28 is a cross-sectional view showing the magnetic disk andthe head slider for Example 16 of the present invention;

[0051]FIG. 29 schematically shows the planar construction of the headslider for Example 16 of the present invention;

[0052]FIG. 30 shows the arrangement of the read head, the write head andthe tracking head relative to the recording track band for Example 16 ofthe present invention;

[0053]FIGS. 31A to 31D are cross-sectional views showing a method ofmanufacturing the charge-storing recording medium for Example 17 of thepresent invention;

[0054]FIG. 32 is a cross-sectional view showing the charge-storingrecording medium and the head slider for Example 17 of the presentinvention; and

[0055]FIG. 33 schematically shows the planar construction of the headslider for Example 17 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0056]FIG. 1 is a plan view showing the construction of the recordinglayer formed on a substrate included in the recording medium accordingto one embodiment of the present invention. As shown in the drawing, aplurality of recording track bands 1 is formed in the recording layer,the recording track bands 1 being separated from each other by band-likeisolation regions 2. The shape of the entire recording medium is notparticularly limited in the present invention. It is possible for theentire recording medium to be shaped like a disk or like a card. In thecase of a disk-type recording medium, it is desirable to form therecording track bands 1 concentrically or spirally, where the trackdirection is the circumferential direction. On the other hand, in thecase of a card-type recording medium, it is desirable to form linearlythe recording track bands 1.

[0057] In the recording track band 1, regularly arrayed recording cellsare separated from each other by a matrix 12 formed of a non-recordingmaterial. The material of the matrix 12 is not particularly limited, asfar as information written in the recording cells 11 is not destroyed.For example, it is possible to use an inorganic insulating material suchas SiO₂ or Al₂O₃, or an organic insulating material such as a polymer asthe material of the matrix 12.

[0058] The recording cells 11 are periodically arrayed in the trackdirection with a pitch P so as to form a sub-track, and a plurality rowsof sub-tracks are included in a single recording track band 1. In FIG.1, four rows of the sub-tracks la to id are included in the singlerecording track band 1. As apparent from FIG. 1, nearest neighboring tworecording cells, each positioned on adjacent two sub-tracks, for examplethe sub-track 1 a and 1 b, are formed apart from each other at a pitchP/n in the track direction, where 2≦n≦5. Namely, the distance in thetrack direction between the center of the recording cell 11 in thesub-track 1 a and the center of the adjacent recording cell 11 in thesub-track 1 b is equal to 1/n, where 2≦n≦5, of the pitch P of therecording cells in one sub-track. In FIG. 1, the recording cells 11 formthe most stable structure of the hexagonal close-packed structure so asto form a triangular lattice. Therefore, the nearest neighboring tworecording cells 11 included in the adjacent sub-tracks are deviated byP/2 from each other in the track direction.

[0059] In the recording medium of the particular construction, itsuffices for the recording cells 11 to be regularly arrayed with packedin a high-density within a limited region of the recording track band 1,not within the entire surface of the substrate. It follows that it ispossible to manufacture the recording medium stably and with a low costby using self-ordering particles.

[0060] Note that, if n is larger than 2, the possibility ofsuperposition of the recording cells positioned on the adjacentsub-tracks in the track direction is made high. In this case, it isnecessary to reduce the size of the recording cells in order todiscriminate the recording cells positioned on the adjacent sub-tracks.On the other hand, when n equals to 2, it is easy to discriminate therecording cells positioned on the adjacent sub-tracks even if the sizeof the recording cells is made large.

[0061] It is desirable for the recording cell size to fall within arange of between 2 nm and 100 nm. It is more desirable for the recordingcell size to fall within a range of between 2 nm and 20 nm, because therecording density is increased as the recording cell size is reduced.The recording cells have substantially the same size. It is alsodesirable for the pitch P between the recording cells to fall within arange of between 2 nm and 100 nm. Note that, the pitch P between therecording cells is larger than the recording cell size so that therecording cells are separated from each other. It is also desirable forthe recording cell to be circular, elliptical, oblong or square in itscross section because the recording cells can be packed in ahigh-density. Particularly, it is desirable for the recording cell to becircular because the circular recording cells can be formed easily bythe self-ordering. Further, it is desirable for the recording cell tohave a hexagonal close-packed structure. It should be noted in thisconnection that the hexagonal close-packed structure is the most stablestructure in the self-ordering of the fine particles. In addition, therecording cells having the hexagonal close-packed structure have thesmallest defects and can be manufactured at a low cost.

[0062] It is possible for the isolation region 2 arranged between theadjacent recording track bands 1 to be formed of a non-recordingmaterial or a recording material equal to that of the recording cells.

[0063] If the isolation region 2 is formed of a non-recording material,seek operation for the recording track band can be easily performed byutilizing the phenomenon that a region where no signal is providedappears periodically every time the read head crosses a plurality ofrecording track bands.

[0064] If the isolation region 2 is formed of a recording material equalto that of the recording cells, it is possible to detect trackingsignals from the isolation region 2 and to record address informationfor the recording track band in the isolation region 2.

[0065] In the recording medium of the present invention, it is possiblefor the regular array of the recording cells to be formed in all theregions where information is written. It is also possible that addresssignal regions are formed in advance and the regularly arrays of therecording cells to be formed as data regions. Further, it is possiblefor the regular arrays of the recording cells to be formed in advance inonly the servo mark regions for tracking. In this case, it is possibleto form, for example, a multigrain magnetic thin film in the regionswhere information is written or from which information is read out. Inrecent years, a long time is required for servo writing and, thus, themethod of forming servo marks in advance is highly effective.

[0066] The recording principle of the recording medium used in theembodiments of the present invention is not particularly limited. Inother words, recording media based on various recording principles canbe used in the embodiments of the present invention. For example, therecording medium includes a magnetic recording medium, a phase changeoptical recording medium, a ferroelectric medium, a charge-storingmedium or a recording medium containing an organic dye of a fluorescentcompound. Preferable recording medium is the magnetic recording mediumor the phase change optical recording medium. Particularly preferablerecording medium is a perpendicular magnetic recording medium capable ofachieving a high recording density.

[0067] Magnetic recording materials include, for example, crystallinematerials such as Ni—Fe and Fe—Al—Si, Co-based amorphous materials suchas Co—Zr—Nb, and Fe-based microcrystalline materials such as Fe—Ta—N, aswell as Fe, Co, Fe—Co, Fe—Pt, Co—Pt, Co—Cr, Co—Ni, Ba ferrite and Cooxide.

[0068] Inorganic phase change optical recording materials include, forexample, Sb—Se, Sb—Te, Ga—Se, Te—Se—Sb, Te—Ga—Se, Te—Ge—Sn, Te—As—Ge,Cs—Te, Ge—Sb—Te, Ag—In, and In—Sb—Te.

[0069] Recording materials for the charge-storing media include a metal,a semiconductor, a conductive polymer, and an organic dye. Thecharge-storing medium has a structure that an underlying electrode, aninsulating layer and a recording layer are formed on a substrate.

[0070] Organic dyes are used for various recording media and include,for example, a dye for the electric charge recording, a dye for thephase change recording, a dye for the write-once type recording, aphotochromic dye, a fluorescent dye, and a photorefractive dye. Whererecording is performed based on the presence or absence of electriccharges by using an organic dye medium, used are dye molecules havingdonor or acceptor properties. In the case of performing recording on thebasis of the phase change between the crystalline state and theamorphous state, used are dye molecules having a high crystallizationspeed. The write-once type dye is a material which is irreversiblychanged upon light absorption or which irreversibly changes thesurrounding upon light absorption. Where fluorescence is used forreading, it is desirable to use a fluorescent dye emitting intensefluorescence. It is also possible to use a photochromic compound as anorganic dye whose absorption is changed by light. Specific examples oforganic dyes are disclosed in, for example, Japanese Patent ApplicationLaid-open Publication No. 11-328725.

[0071] Fluorescent compounds include both an organic fluorescentcompound and an inorganic fluorescent compound. In general, fluorescentlife of the inorganic compound is longer than that of the organiccompound and, thus, it is desirable to use the organic compound forhigh-speed reading.

[0072] Photochromic compounds include, for example, spirooxazines,diarylethenes, fulgides, indigos, spiropyrans, cyclophans, chalcones,and condensed polycyclic compounds.

[0073] A method for manufacturing a recording medium according toembodiments of the present invention comprises: forming on a substrate acontinuous or intermittent groove region, or a band region containing aspecified chemical component, which corresponds to a recording trackband; forming a two-dimensional regular array structure of self-orderingmolecules or fine particles in the groove region or the band region; andforming recording cells corresponding to the regular array structure.

[0074] In the case of using a groove structure having an irregularity,it is possible to realize a regular array along the groove byinterrupting a crystal domain of self-ordering particles on the steppedportion of the irregularity.

[0075] In the case of using the band region prepared by patterning thespecified chemical compound, it is possible to form regions where theself-ordering particles are adsorbed and are not adsorbed by selectingappropriately the chemical surface state of the self-ordering particlesand the surface state of the chemical component of the band region. Theregular array takes place only in the portion where the self-orderingparticles are adsorbed so as to make it possible to obtain a regulararray along the band structure. Also, by varying interaction between theself-ordering particles and the surface by a chemical pattern, it ispossible to obtain a desired regular array only on a chemical pattern inwhich certain interaction takes place while failing to obtain a regulararray on another chemical pattern so as to lead to a random arrangement.It is preferable to make the width of the band structure sufficientlysmaller than the size of the regular array naturally formed by theself-ordering particles in the case where the band structure is notpresent. If the particular condition is satisfied, it is possible toform the structure in which the self-ordering particles are regularlyarrayed in the width direction of the band structure.

[0076] It is desirable for the self-ordering particle to have a sizefalling within a range of between 2 nm and 100 nm, more desirablybetween 2 nm and 20 nm. It is also desirable for the self-orderingparticle to be circular, elliptical, oblong or square corresponding tothe shape of the recording cells described above. In particularly, it isdesirable for the self-ordering particle to be circular because thecircular particles can be formed easily by self-ordering.

[0077] Where it is intended to realize a recording density on the orderof Tbpsi by the recording medium according to embodiments of the presentinvention, the width of the groove structure or the band structure isdetermined as follows. Where, for example, two rows of recording cellsare present in a single recording track band, the width of the groovestructure or the band structure is about 40 nm, which is the size thatcan be formed by ordinary electron beam lithography. Since more than tworows of sub-tracks can be actually formed in a single recording trackband, it is possible to utilize lithography techniques which are cheaperand permit a higher throughput, but show low resolution. The lithographythat can be utilized in the embodiments of the present inventionincludes, for example, optical lithography, electron beam lithography, amethod using a scanning probe such as an atomic force microscope, ascanning tunneling microscope or a near-field microscope, and anano-imprinting lithography (P. R. Krauss, et al., J. Vac. Sci. Technol.B13 (1995), pp. 2850).

[0078] The self-ordering particles that can be utilized in theembodiments of the present invention include, for example, a blockcopolymer or fine particles of a polymer, a metal, a semiconductor, oran oxide having a size falling within a range of between severalnanometers and 100 nanometers.

[0079] In the case of using a block copolymer, used is a block copolymerhaving a block that can be removed selectively among two or more blocksafter formation of the self-ordering particles. In this case, it isdesirable to utilize difference in etching rate among the blocks in RIEor another etching method.

[0080] In the case of using, for example, a block copolymer comprising apolystyrene block and a polybutadiene block, it is possible to adoptdevelopment such that the polystyrene block alone is left by ozonetreatment. In a block copolymer comprising a polystyrene block and apolymethyl methacrylate block, the polystyrene block exhibits an etchingresistance higher than that of the polymethyl methacrylate block againstreactive ion etching (RIE) using CF₄ as an etchant so as to make itpossible to remove selectively by RIE the polymethyl methacrylate blockand the recording layer under the polymethyl methacrylate block (K.Asakawa et al., APS March Meeting, 2000).

[0081] The block copolymers utilized in the embodiments of the presentinvention include, for example,polybutadiene-block-polydimethylsiloxane, polybutadiene-block-4-vinylpyridine, polybutadiene-block-methyl methacrylate,polybutadiene-block-poly-t-butyl methacrylate,polybutadiene-block-poly-t-butyl acrylate, poly-t-butylmethacrylate-block-poly-4-vinyl pyridine, polyethyleneblock-polymethylmethacrylate, poly-t-butyl methacrylate-block-poly-2-vinyl pyridine,polyethylene-block-poly-2-vinyl pyridine,polyethylene-block-poly-4-vinyl pyridine,polyisoprene-block-poly-2-vinyl pyridine, polymethylmethacrylate-block-polystyrene, poly-t-butylmethacrylate-block-polystyrene, polymethyl acrylate-block-polystyrene,polybutadiene-block-polystyrene, polyisoprene-block-polystyrene,polystyrene-block-poly-2-vinyl pyridine, polystyrene-block-poly-4-vinylpyridine, polystyrene-block-polydimethyl siloxane,polystyrene-block-poly-N,N-dimethyl acrylamide,polybutadiene-block-polysodium acrylate,polybutadiene-block-polyethylene oxide, poly-t-butylmethacrylate-block-polyethylene oxide, polystyrene-block-polyacrylate,and polystyrene-block-polymethacrylate. In addition to these AB-typediblock copolymers exemplified above, it is also possible to useABA-type triblock copolymers.

[0082] In the case of using a block copolymer, it is desirable to usethose having a component ratio that permits forming a micellar structureor a cylinder structure on the substrate surface. In this case, it ispossible to form circular recording cells separated from each other andarrayed regularly. It is possible to form a film of the block copolymerby, for example, spin coating of a solution prepared by dissolving theblock copolymer in a suitable solvent such as toluene. In general, phaseseparation of the block copolymer into a self-ordering array can beobtained by applying annealing treatment under temperatures not lowerthan the glass transition point of the material.

[0083] In the case of using fine particles made of a polymer or a metaland having a size of scores of nanometers, a self-ordering regular arraycan be formed by applying a solution including the fine particlesdispersed therein from above a disk having a band structure formedtherein, followed by drying the solution so as to remove the solvent andsubsequently removing excessively adsorbed fine particles by using asuitable solvent. It is also possible to form a regular array by dippinga disk substrate in a solution including fine particles dispersedtherein for a certain time so as to permit the fine particles to beadsorbed on the disk substrate.

[0084] After formation of the regular array of the self-orderingparticles by the method described above, it is possible to form rows ofrecording cells, which are regularly arranged as desired, by etching theunderlying recording layer formed in advance by means of, for example,ion milling with the self-ordering particles used as a mask. In order toetch off the recording layer with a high aspect ratio, it is effectiveto form a film of SiO₂ or Si between the recording layer and theself-ordering particle layer, followed by transferring the regular arraypattern of the self-ordering particles by, for example, RIE onto thefilm of SiO₂ or Si and subsequently processing the recording layer.Since the film of SiO₂ or Si can be etched off by RIE with a high aspectratio, it is possible to etch the recording layer with a high aspectratio by using the film of SiO₂ or Si as a mask.

[0085] As described above, it is possible to manufacture patterned mediahaving recording cells buried in a matrix by covering the regular arrayof the recording cells with a matrix material and by polishing thesurface so as to planarize the surface.

[0086] It is also possible to form recording cells by forming regularlyarrayed fine pores in a matrix with the self-ordering particles used asa mask, followed by filling the pores with a recording material. In thiscase, a film of a matrix material is formed first on a disk substrate.Then, formed is a resist layer for forming a groove structure forcontrolling the array of the self-ordering particles or for forming aband structure prepared by patterning a specified chemical component.Further, a groove structure or a band structure is formed in the resistlayer by lithography. After formation of a film for self-orderingparticles, annealing treatment is applied for providing regularlyarrayed particles. Further, etching treatment is applied with theself-ordering particles used as a mask so as to form holes in thematrix. After removal of the resist layer, the holes are filled with arecording material. It is possible to remove the resist layer after thedeposition of the recording material. It is also possible to leave theresist layer without removing for use as it is.

[0087] It suffices for the resist material not to destroy the recordinglayer, to be capable of forming a structure by lithography, and not tobe damaged by formation of a film for self-ordering particles and bytreatment for the regular array. Examples of self-ordering particlesinclude those formed from a block copolymer and fine particles of apolymer, a metal, a semiconductor or an oxide having a size of scores ofnanometers. It is also possible to use a fine pore array of Al₂O₃ formedby anodic oxidation applied to Al.

[0088] In the case of using a block copolymer, used is a block copolymerfrom which the block forming a micell or a cylinder can be removedselectively for forming holes in the matrix material.

[0089] In the case of using fine particles formed of a polymer or ametal, a negative pattern of the pattern formed of the fine particles isused as a mask for forming holes in the matrix material. To be morespecific, after deposition of a material capable of forming an etchingmask such as a metal on the fine particle array, the fine particles areremoved so as to expose the underlying matrix layer only in the portionswhere the fine particles have been present and to process the exposedportions of the underlying matrix layer.

[0090] In the case of using a fine pore array of Al₂O₃ formed by anodicoxidation applied to Al, an Al film is formed on a band structure of afilm in which a matrix is exposed in a concave portion, followed byremoving the film and the Al film thereon so as to obtain a bandstructure of Al. Then, the band structure of Al is subjected to anodicoxidation so as to obtain a fine pore array of Al₂O₃ regularly arrayedwithin the band structure. Further, the fine pore array is transferredto the underlying matrix with the fine pore array of Al₂O₃ used as amask.

[0091] Also, in the case of using a fine pore array of Al₂O₃, it ispossible to use the fine pore array of Al itself as a matrix. In thiscase, after formation of an Al film, formed is a pattern of a film inwhich Al is exposed in the concave portion of the groove structure. Ifthe pattern thus formed is subjected to anodic oxidation, the reactionproceeds only in the portion where Al is exposed so as to obtain a finepore array of Al₂O₃ arrayed along the band structure.

[0092] Also, a position-controlled fine pore array can be formed inanodic oxidation of Al by imparting in advance fine pores to the surfaceto be subjected to the anodic oxidation. It is also possible tomanufacture a regularly arrayed Al₂O₃ fine pore array by forming agroove structure on an Al film, by forming regularly arrayed fine poreson the Al surface by etching with a self-ordering film such as a blockcopolymer used as a mask, and by subjecting the Al to anodic oxidationafter removal of the self-ordering film.

[0093] It is possible to obtain separated recording cells by forming afilm of a recording material on the regular array of fine pores formedin the matrix, followed by polishing the film of the recording materialthus formed.

[0094] Further, it is possible to employ a method of preparing a stampmaster having irregularity by the method using the self-orderingparticles, followed by transferring the pattern to a disk substrate bynano-imprinting lithography utilizing the stamp master.

[0095] In the first step, formed on a substrate is a resist layer forforming a groove structure for controlling the array of theself-ordering particles or for forming a band structure by pattering aspecified chemical component. Then, a groove structure or a bandstructure is formed in the resist layer by lithography. After formationof a film for self-ordering particles, a regular array is formed by, forexample, annealing treatment. Further, etching is applied with theself-ordering particles used as a mask so as to prepare a stamp master.On the other hand, a resist film used as a mask is formed on a substratehaving a recording layer or a matrix film formed thereon. The pattern ofthe stamp master is transferred to the resist film by pressing the stampmaster against the resist film while heating the stamp master. Then, arecording medium is obtained via a process of forming a recording cellarray or a fine pore array within the matrix by etching.

[0096] It is also possible to employ a manufacturing method in whichfine particles formed of a recording material are arranged directlywithin a band structure so as to use the fine particles as the recordingcells. It is possible to form a self-ordering regular array by applyinga solution including fine particles of a recording material dispersedtherein from above a substrate having a band structure formed therein,followed by drying the solution so as to remove the solvent andsubsequently removing excessively adsorbed fine particles by using asuitable solvent. It is also possible to form a regular array by dippinga substrate in a solution including fine particles dispersed therein fora certain time so as to permit the fine particles to be adsorbed on thesubstrate. After formation of the recording cells in this fashion, it ispossible to manufacture a recording medium by covering the recordingcells with a binder or a material forming a protective film so as toprevent the fine particles from being peeled off the substrate.

[0097] In the method described above, it is possible to regularly arraythe self-ordering particles over a large area along the band structureby applying a re-arraying treatment such as annealing treatment. Whereit is difficult to apply such a re-arraying treatment, it is possible toobtain a regular array structure in which particles are perfectlyaligned in a desired direction within the band structure of a small areaby intermittently forming an irregular structure or a chemical patternin the longitudinal direction of the band. In other words, it ispossible to form a two-dimensional crystal structure of theself-ordering particles, which is of a completely uniform structure freefrom grain boundaries within the band structure having a predeterminedlength.

[0098] A recording apparatus according to one embodiment of the presentinvention comprises: a recording medium comprising a substrate and arecording layer formed on the substrate comprising (a) a recording trackband and (b) recording cells regularly arrayed in the recording trackband to form a plurality rows of sub-tracks, wherein the recording cellsincluded in each sub-track are formed apart from each other at a pitch Pin the track direction, and wherein nearest neighboring two recordingcells, each positioned on adjacent two sub-tracks in the track band, areformed apart from each other at a pitch P/n in the track direction,where 2≦n≦5; a write head; and a read head.

[0099] In the recording apparatus described above, it is possible to usedetection signals themselves generated from the recording cells astracking signals by utilizing the deviation of the recording cells onthe adjacent sub-tracks so as to make it possible to increase a trackingsampling frequency. As a result, it is possible to perform tracking bythe read head even if the size of the recording cells is made 100 nm orless. Also, since it is possible to lower the error rate, it is possibleto widen data regions.

[0100] The regular array by self-ordering forms a close-packed structureand, thus, forms a triangular lattice in many cases. If the regulararray of the triangular lattice is formed in the track direction, therecording cells on the two adjacent sub-tracks are deviated from eachother in the track direction such that the distance between the centerof the recording cell in one sub-track and the center of the recordingcell in the adjacent sub-track is rendered equal to ½ of the pitch P ofrecording cells forming a single line of the sub-track. It follows that,where a read head large enough to cover the two adjacent sub-tracks isused, it is possible to detect alternately reproduce signals generatedfrom the two sub-tracks and to distinguish the reproduce signals thusdetected. This implies that it is possible to double the effective trackdensity, which is effective for increasing a track density.

[0101] The recording apparatus according to another embodiment of thepresent invention is configured to write to and read from a recordingmedium comprising a substrate and a recording layer formed on thesubstrate comprising (a) a recording track band and (b) recording cellsregularly arrayed in the recording track band to form a plurality rowsof sub-tracks, wherein the recording cells included in each sub-trackare formed apart from each other at a pitch P in the track direction,and wherein nearest neighboring two recording cells, each positioned onadjacent two sub-tracks in the track band, are formed apart from eachother at a pitch P/n in the track direction, where 2≦n≦5. The recordingapparatus comprises a write head, a read head, and a controllercontrolling write timing signals supplied to the write head inaccordance with signals generated from the read head.

[0102] The recording apparatus is capable of preventing the write headfrom writing to a region where no recording cell is present.

[0103] The aforementioned controller controls the write timing signalssupplied to the write head, for example, by comparing (a) a timeinterval determined by the pitch of the recording cells regularlyarrayed in the track direction and a traveling speed of the read headwith (b) a time interval of signals generated from the read head.

[0104] In the recording apparatus having such a controller, it ispossible to write while avoiding a defective region even if there is thedefective region in the regular array by self-ordering so as to bringabout discontinuity in the sub-track formed within the recording trackband.

[0105] To be more specific, in the recording apparatus, the recordedinformation is read out at a time interval T determined by the latticedistance of the recording cells and the traveling speed of the head(relative speed between the read head and the recording medium) in theregion where the recording cells are regularly arrayed. However, thetime interval of the signals read by the read head is disturbed in thedefective region of the recording cells. Therefore, in this case, thesignals read by the head is not processed as information temporarily.When the signal generation is started again at the time interval T, thesignals read out at that time are processed again as information, andwriting is also started again.

[0106] It is possible to set arbitrarily the criteria for judging thatthe read head is traveling over a defective region on the basis of thedisturbance in the time interval of the signals generated from the readhead. For example, it is judged that the read head is traveling over adefective region in the case where signals are detected in anunreasonable time interval at least two or three times so as to generateread errors. Also, it is possible to use as the measure for judgment thecase where signals are generated from the read head in a time intervalshorter by at least 30% than the reference time interval T and the casewhere signals are not generated even after the lapse of time longer byat least 30% than the reference time interval T. In this case, it ispossible to use as the measure for judgment the case where such aphenomenon has taken place once or the case where the signals aredisturbed a plurality of times during the time 2T or 3T.

[0107] It is also possible to set arbitrarily the criteria for judgmentthat the read head has started again to travel over the regularlyarrayed region. For example, it is judged that the read head istraveling over the regularly arrayed region in the case where signalhave been generated at an interval within ±30% of the time interval Tfrom the moment when a certain signal has been obtained. In this case,it is possible to use as the measure for the judgment the case where theparticular phenomenon has taken place once or the case where signalshave been obtained at a time interval T during the time 2T or 3T.

[0108] Where information is written, a defective region should berecognized before writing, and the writing is started again from thesubsequent regular array region while avoiding the defective region. Itfollows that it is necessary for the read head to recognize the positionof recording cells before the write head writes information in therecording cells. For allowing the read head to recognize the position ofthe recording cells, it is possible to arrange the read head forward ofthe write head in the track direction. Also, when it comes to anintegrated head for reading and writing, it is possible to operate thehead such that the head accesses the recording medium a plurality oftimes at the same track position so as to read the position of therecording cells, followed by writing information.

[0109] In the recording apparatus described above, it is possible forthe write head to be shaped substantially similar to the recording cell.If the shape of the write head is made similar to the shape of therecording cell, it is possible to prevent cross-write among therecording cells and to improve writing efficiency. Since it is desirablefor the recording cell to be circular, it is also desirable for thewrite head to be circular and to have a size equal to that of therecording cell. However, it is also possible for the write head to beshaped square having rounded corners or not having rounded corners aslong as it is sized small enough to be contained in the circle of therecording cell.

[0110] It is possible for the recording apparatus according to anotherembodiment of the present invention to include a read head for trackingseparately from the read head for reading information. The read head fortracking is used for the tracking of the read head for readinginformation and the write head by using the detection signals fromregions other than the data region being read out as a tracking signalso as to achieving tracking more precisely and at a high speed.

[0111] In the case of a magnetic recording apparatus, the read head isformed of a magnetic sensor such as GMR, and the write head is formed ofa magnetic head. In the case of a phase change optical recordingapparatus, the read head is formed of an optical sensor for detectingdifference in reflectance, and the write head is formed of a heat sourcehead such as an optical head or an electron beam head.

[0112] In the case of an optically (or thermally)-assisted magneticrecording apparatus, a source for irradiating an electron beam or anear-field light as an auxiliary of the write magnetic head is used. Theelectron beam or the near-field light, which permits the irradiationspot to be made particularly small, is particularly useful forhigh-density recording.

[0113] In the case of an apparatus for a charge-storing medium, a chargesensor such as a field effect transistor (FET) may be used as a readhead. For a charge-storing medium of particularly high recordingdensity, use of a single electron transistor (SET) permits highlysensitive detection of charges. As a write head, an electron emissionsource made of, for example, a metal or a semiconductor. In writingoperation, an electric field is applied between the write head and theunderlying electrode formed under the recording layer (domain) of thecharge-storing medium, thereby injecting charges to the recordingdomain. In erasing operation, a reverse electric field is applied toinject charges having reverse polarity to those used in the writingoperation, or charges stored in the recording domain are withdrawn,thereby erasing recording.

EXAMPLES

[0114] The present invention will now be described in more detail withreference to Examples of the present invention. Needless to say, thepresent invention is not limited to the following Examples.

Example 1

[0115] In this Example, a recording track band is formed by regularlyarraying a block copolymer in a groove region formed on a substrate. Amethod of manufacturing a magnetic recording medium for this Examplewill now be described with reference to FIGS. 2A to 2D.

[0116] As shown in FIG. 2A, a groove structure is formed on a substrateas follows. Specifically, a magnetic layer 22 is formed by forming a Pdunderlayer having a thickness of about 30 nm and a layer of aperpendicular magnetic recording material of Co—Cr—Pt having a thicknessof about 50 nm on a glass disk substrate 21 having a diameter of 2.5inches, followed by forming a SiO₂ film 23 having a thickness of about50 nm on the magnetic layer 22. Then, a resist film 24 is formed on theSiO₂ film 23 by spin coating. Further, the resist film 24 is processedby optical lithography so as to form a resist pattern that is shapedsuch that a spiral groove 25 having a width of about 200 nm is definedby a convex portion having a width of about 200 nm. The SiO₂ film 23 isetched to reach the magnetic layer 22 by RIE with the resist patternused as a mask so as to transfer the groove 25 to the SiO₂ film 23. Thegroove region thus formed provides a recording track band. Also, themagnetic layer 22 below the resist pattern is used as the isolationregion.

[0117] As shown in FIG. 2B, the groove region is filled with a blockcopolymer so as to form a regularly arrayed structure of fine particlesas follows. Specifically, hydrophobic treatment is applied to thesurface of the magnetic layer 22 with hexamethyldisilazane, followed byashing the residue of the resist pattern. On the other hand, prepared isa solution of 1% w/w by dissolving polystyrene (PS)-polybutadiene (PB)block copolymer in toluene, PS having a molecular weight Mw of 10,000and PB having a molecular weight Mw of 40,000. The substrate is coatedwith the solution thus prepared by spin coating so as to bury the blockcopolymer 26 in the groove region transferred to the SiO₂ film 23. Thesubstrate is annealed at 150° C. for 30 hours under vacuum so as toregularly array the block copolymer 26. As a result, formed is astructure in which island-like polystyrene particles 27 are surroundedby a sea-like polybutadiene portion 28.

[0118] As shown in FIG. 2C, recording cells are formed with using theregularly arrayed fine particles as a mask. After the block copolymer 26is treated with ozone so as to remove the polybutadiene portion 28,followed by washing with water. Further, recording cells 29 are formedby etching the magnetic layer 22 by Ar ion milling with using theresidual polystyrene particles 27 as a mask.

[0119] Finally, as shown in FIG. 2D, a matrix is formed in the spacebetween the recording cells, followed by planarizing the surface of thematrix as follows. Specifically, the residue of the polystyreneparticles are subjected to ashing, followed by forming a SiO₂ filmhaving a thickness of about 50 nm on the entire surface so as to fillthe space between the recording cells 29, thereby forming a matrix 30.The surface of the SiO₂ film is subjected to chemical mechanicalpolishing (CMP) so as to planarize the surface. Then, a diamond-likecarbon film is formed on the entire surface so as to form the protectivefilm 31.

[0120]FIG. 3 schematically shows the result of observation of themagnetic recording medium thus manufactured with a magnetic forcemicroscope. As shown in FIG. 3, recording track bands 1 each having awidth of about 200 nm and isolation regions 2 each formed of a magneticlayer having a width of about 200 nm are formed alternately. Therecording cells 29 are separated from each other by the matrix 30 withina single recording track band 1 so as to form a hexagonal close-packedstructure and, thus, to form a triangular lattice. The recording cells29 each having a size of 30 nm are periodically arrayed with a pitch Pin the track direction so as to form a sub-track, and six rows of thesub-tracks 1 a to if are included in each recording track band. Sincethe recording cells 29 form a triangular lattice as described above,nearest neighboring two recording cells 29 positioned on adjacent twosub-tracks are deviated in the track direction such that the distance inthe track direction between the center of the recording cell 29 in onesub-track and the center of the adjacent recording cell 29 in theadjacent sub-track is equal to ½ of the pitch P of the recording cellsforming the sub-track.

Example 2

[0121] In this Example, a recording track band is formed by regularlyarraying a block copolymer in a band region containing a specifiedchemical substance formed on a substrate.

[0122] In the first step, a magnetic layer is formed on a substrate asin Example 1, followed by forming a SiO₂ film having a thickness ofabout 10 nm on the magnetic layer and subsequently forming a resist filmon the SiO₂ film. As in Example 1, the resist film is processed byoptical lithography so as to form a resist pattern such that a spiralgroove having a width of about 200 nm is defined by a convex portionhaving a width of about 200 nm. After the surface of the exposed SiO₂film is subjected to hydrophobic treatment withoctadecyltrimethoxysilane, followed by removing the resist pattern. As aresult, formed on the surface of the SiO₂ film are a hydrophilic bandregion (isolation region) which is not subjected to the hydrophobictreatment and a hydrophobic band region (recording track band) modifiedby alkyl chains subjected to the hydrophobic treatment. As in Example 1,a solution of a polystyrene-polybutadiene block copolymer is spin coatedso as to permit the block copolymer to be selectively adsorbed on thehydrophobic band region. The block copolymer is annealed so as to form aregular array. As a result, formed is a structure in which island-likepolystyrene particles are surrounded by a sea-like polybutadieneportion.

[0123] The block copolymer is treated with ozone so as to remove thepolybutadiene portion, followed by washing with water. The SiO₂ film isetched by reactive ion etching with using the residual polystyreneparticles as a mask so as to transfer the pattern of the polystyreneparticles. Further, recording cells are formed by etching the magneticlayer by Ar ion milling with using the pattern of the residual SiO₂ filmas a mask.

[0124] As in Example 1, a SiO₂ film as the matrix is formed on theentire surface so as to fill the space between the recording cells,followed by polishing the surface of the SiO₂ film by chemicalmechanical polishing (CMP) so as to planarize the surface. Then, adiamond-like carbon film is formed on the entire surface so as to form aprotective film.

[0125] The magnetic recording medium thus manufactured is observed witha magnetic force microscope. Recording track bands each having a widthof about 200 nm and isolation regions each formed of the SiO₂ filmhaving a width of about 200 nm are formed alternately. The recordingcells are found to form a hexagonal close-packed structure and, thus, toform a triangular lattice in a single recording track band. Therecording cells each having a size of 30 nm are periodically arrayedwith a pitch P in the track direction so as to form a sub-track, and sixrows of the sub-tracks are included in each recording track band. Thenearest neighboring two recording cells positioned on two adjacentsub-tracks are deviated such that the distance in the track directionbetween the center of the recording cell in one sub-track and the centerof the adjacent recording cell in the adjacent sub-track is equal to ½of the pitch P of the recording cells forming the sub-track.

Example 3

[0126] A glass substrate is spin coated with a resist film containing anovolak resin as a base resin. The resist film is processed by opticallithography and development with a TMAH aqueous solution, followed bybaking the resist film at 150° C. to cure the resin so as to form aresist pattern such that a spiral groove having a width of about 200 nmis defined by a convex portion having a width of about 200 nm and aheight of about 40 nm.

[0127] Prepared is a solution by dissolving 2 parts by weight ofpolystyrene (PS)-polymethyl methacrylate (PMMA) block copolymer (PShaving a molecular weight Mw of 65,000, PMMA having a molecular weightMw of 13,500, and Mw/Mn being 1.0) in ethyl cellosolve acetate. Thesubstrate is spin coated with the solution thus prepared so as to fillthe groove regions between the resist patterns with the block copolymer.Then, the substrate is annealed so as to regularly array the blockcopolymer. As a result, formed is a structure in which island-like PMMAparticles are surrounded by a sea-like PS portion. Reactive ion etchingis performed to the resultant substrate for 25 seconds by using a CF₄gas under the conditions of the output of 100 W, the flow rate of 30sccm, and the pressure of 0.1 Torr. Under these conditions, PMMA isselectively etched, and the exposed glass substrate is etched with theresidual PS pattern used as a mask. Ashing is performed to the substrateby using an O₂ gas under the conditions of the output of 100 W, the flowrate of 30 sccm, and the pressure of 0.1 Torr so as to remove the PSmask. As a result, formed is a pattern in which pores each having a sizeof 17 nm are arrayed in a close-packed structure within the band regionhaving a width of about 200 nm formed on the glass substrate.

[0128] Based on the preliminary experiment described above, PMMA isselectively etched by RIE using a CF₄ gas, followed by etching theexposed glass substrate with the residual PS pattern used as a mask andsubsequently forming a Co—Cr—Pt film by sputtering. Then, ashing isperformed with using an O₂ gas so as to remove the PS mask.

[0129] The magnetic recording medium thus manufactured is observed witha magnetic force microscope. It has been found that a pattern in whichpores each having a size of 17 nm are arrayed in a manner to form theclose-packed structure within the band region having a width of about200 nm formed on the glass substrate.

Example 4

[0130] In this Example, a recording track band is formed by regularlyarraying metal fine particles in a groove region formed on a substrate.

[0131] In the first step, a magnetic layer, a SiO₂ film having athickness of about 20 nm and an electron beam resist are successivelyformed in the order mentioned on a glass substrate. The resist film isprocessed by electron beam lithography so as to form a resist pattern inwhich a spiral groove having a width of about 100 nm is defined by aconvex portion having a width of about 150 nm. The substrate is dippedin an aqueous gold colloid solution containing fine gold particleshaving a size of 40 nm, followed by rinsing the substrate with purewater. As a result, the fine gold particles are regularly arrayed withinthe groove formed between the resist patterns. Then, the SiO₂ film isetched to the magnetic layer by RIE, followed by further etching themagnetic layer by Ar ion milling. After removal of the SiO₂ film, thesubstrate is observed with an electron microscope. As a result,recording cells each having a size of 40 nm are found to have formed aclose-packed structure within the recording track band having a width ofabout 100 nm so as to form two rows of sub-tracks.

Example 5

[0132] In this Example, a recording track band is formed by regularlyarraying a block copolymer in a groove region formed on a substrate soas to form a matrix having pores, followed by filling the pores with amagnetic recording material. A method of manufacturing a magneticrecording medium for this Example will now be described with referenceto FIGS. 4A to 4D.

[0133] As shown in FIG. 4A, a groove structure is formed on a substrateas follows. Specifically, successively formed on a glass disk substrate41 having a diameter of 2.5 inches are a Pd underlayer having athickness of about 30 nm, an Al₂O₃ film 42 having a thickness of about50 nm, which forms a matrix and a isolation region, and a SiO₂ film 43having a thickness of about 50 nm in the order mentioned. After a resistfilm is formed on the SiO₂ film 43 by spin coating, the resist film isprocessed by optical lithography so as to form a resist pattern in whicha spiral groove having a width of about 200 nm is defined by a convexportion having a width of about 200 nm. Then, the SiO₂ film 43 is etchedwith the resist pattern used as a mask so as to transfer the groove 44.

[0134] As shown in FIG. 4B, the groove region is filled with a blockcopolymer to form a regular array of fine particles as follows.Specifically, prepared is a solution by dissolvingpolystyrene-polymethyl methacrylate block copolymer (PS having amolecular weight Mw of 80,000 and PMMA having a molecular weight Mw of20,000) in a concentration of 1% w/w in toluene. The substrate is spincoated with the solution thus prepared so as to fill the groove regiontransferred to the SiO₂ film 43 with the block copolymer 45. Thesubstrate is annealed at 150° C. for 30 hours under vacuum so as toregularly array the block copolymer 45. As a result, formed is astructure in which island-like polymethyl methacrylate particles 46 aresurrounded by a sea-like polystyrene portion 47.

[0135] As shown in FIG. 4C, a pore structure for the recording cells isformed as follows. Specifically, the block copolymer 45 is treated withan ultraviolet ray so as to decompose the polymethyl methacrylate chain,followed by washing with water. Then, a Cr layer 48 is formed by anoblique vapor deposition. The SiO₂ film 43 is selectively etched by RIEwith the Cr layer used as a mask so as to form pores extending to reachthe Al₂O₃ film 42, followed by transferring the pores 49 to the Al₂O₃film 42 by Ar ion milling so as to form a matrix consisting of the Al₂O₃film 42.

[0136] Further, as shown in FIG. 4D, recording cells are formed asfollows, followed by planarizing the surface. Specifically, a film of aperpendicular magnetic recording material Co—Cr—Pt is formed in athickness of about 50 nm so as to fill the pores 49, thereby formingrecording cells 50, followed by polishing the surface by CMP so as toplanarize the surface. Then, a film of a diamond-like carbon is formedon the entire surface so as to form the protective film 51.

[0137]FIG. 5 schematically shows the result of observation of themagnetic recording medium thus manufactured with a magnetic forcemicroscope. As shown in FIG. 5, recording track bands 1 each having awidth of about 200 nm and isolation regions 2 each formed of the Al₂O₃film 42 having a width of about 200 nm are formed alternately. Therecording cells 50 form a hexagonal close-packed structure and, thus, toform a triangular lattice within a single recording track band 1. Therecording cells 50 each having a size of 30 nm are periodically arrayedwith a pitch P in the track direction so as to form a sub-track, and sixrows of the sub-tracks 1 a to if are included in each recording trackband 1. The nearest neighboring two recording cells 50 positioned onadjacent two sub-tracks are deviated such that the distance in the trackdirection between the center of the recording cell 50 in one sub-trackand the center of the adjacent recording cell 50 in the adjacentsub-track is equal to ½ of the pitch P of the recording cells formingthe sub-track.

Example 6

[0138] In this Example, intermittent recording track bands are formedwith employing the method similar to that employed in Example 5 and byseparating the recording track band in a predetermined length in thetrack direction.

[0139] Specifically, as in Example 5, an Al₂O₃ film having a thicknessof about 50 nm and a SiO₂ film having a thickness of about 40 nm areformed successively on a glass disk substrate. After a resist film isformed on the SiO₂ film by spin coating, the resist film is processed byoptical lithography so as to form a resist pattern in which a spiralgroove having a width of about 140 nm is defined by a convex portionhaving a width of about 200 nm and the inner region of the groove isseparated by a convex portion having a width of about 100 nm so as toform groove regions each having a length of 100 μm. Then, the SiO₂ filmis etched with the resist pattern used as a mask so as to transfer thegroove.

[0140] As in Example 5, the groove region of the SiO₂ film is filledwith a PS-PMMA block copolymer, followed by annealing so as to regularlyarray the block copolymer. Then, pores extending to reach the Al₂O₃ filmare formed by RIE, followed by transferring the pores to the Al₂O₃ filmby Ar ion milling so as to provide a matrix formed of the Al₂O₃ film.

[0141] As a result of observation with an electron microscope, it hasbeen found that the pores are completely arrayed to form four rows ofsub-tracks within the intermittent recording track bands each having alength of 100 μm and a width of about 140 nm. It has also been foundthat completely arrayed pores are formed on the entire surface of thedisk. Then, formation of a film of a magnetic recording material,planarizing of the formed film and formation of a protective film areperformed so as to manufacture a magnetic recording medium.

Example 7

[0142] In this Example, a recording track band is formed by regularlyarraying a block copolymer in a groove region formed on a substrate,followed by forming a matrix having pores by utilizing anodic oxidationof Al and subsequently filling the pores of the matrix with a magneticrecording material.

[0143] To be more specific, an Al film having a thickness of about 50 nmand a SiO₂ film having a thickness of about 50 nm are formedsuccessively one upon the other on a glass disk substrate. After aresist film is formed on the SiO₂ film by spin coating, the resist filmis processed by optical lithography so as to form a resist pattern inwhich a spiral groove having a width of about 200 nm is defined by aconvex portion having a width of about 300 nm. Then, the SiO₂ film isetched with the resist pattern thus formed used as the mask.

[0144] The groove region of the SiO₂ film is filled with a PS-PMMA blockcopolymer (PS having a molecular weight Mw of 120,000 and PMMA having amolecular weight Mw of 30,000), followed by annealing so as to regularlyarray the block copolymer. Then, Ar ion milling is applied directly soas to form pores in the block copolymer, followed by slightly etchingthe surface of the Al film so as to form recesses providing initiatingpoints for anodic oxidation. Further, the residual block copolymer isremoved by using acetone, followed by performing anodic oxidation in asulfuric acid bath under a voltage of 25 V so as to form a matrixconsisting of Al₂O₃.

[0145] As a result of observation with an electron microscope, it hasbeen found that the pores each having a size of 30 nm are arrayed toform four rows of sub-tracks within the recording track band each havinga width of about 200 nm. Then, formation of a film of a magneticrecording material, planarizing of the formed film and formation of aprotective film are performed so as to manufacture a magnetic recordingmedium.

Example 8

[0146] In this Example, a master disk is prepared, and a recordingmedium is manufactured by employing a nano-imprinting technology. Amethod of manufacturing a master disk will now be described withreference to FIGS. 6A to 6C. Also, a method of manufacturing a magneticrecording medium according to this Example will now be described withreference to FIGS. 7A to 7D.

[0147] As shown in FIG. 6A, a groove structure is formed on a substrateas follows. In the first step, a Ti film 62 having a thickness of about50 nm and a SiO₂ film 63 having a thickness of about 50 nm aresuccessively formed on a silicon disk substrate 61. The SiO₂ film 63 ispatterned so as to define a spiral groove 64 having a width of about 200nm by a convex portion having a width of about 200 nm.

[0148] As shown in FIG. 6B, a regular array structure of fine particlesis formed within the groove region as follows. Specifically, the grooveregion of the SiO₂ film 63 is filled with a PS-PB block copolymer (PShaving a molecular weight Mw of 30,000 and PB having a molecular weightMw of 120,000). The substrate is annealed so as to regularly array theblock copolymer 65. As a result, formed is a structure in whichisland-like polystyrene particles 66 are surrounded by a sea-likepolybutadiene portion 67.

[0149] As shown in FIG. 6C, Ti pillars corresponding to recording cellsare formed as follows with the regularly arrayed fine particles used asa mask. Specifically, the block copolymer 65 is treated with ozone so asto remove the polybutadiene portion 67, followed by washing with water.Then, the Ti layer 62 is etched by Ar ion milling with the residualpolystyrene particles 66 used as a mask. Further, the SiO₂ 63 is removedby treatment with a hydrofluoric acid. The master disk thus prepared isobserved with an electron microscope, finding that Ti pillars 68 eachhaving a size of 30 nm are regularly arrayed to form six rows within thegroove region.

[0150] As shown in FIG. 7A, a glass disk substrate 71 is spin coatedwith a resist film 72. Then, a master disk 61 is pressed to the glassdisk substrate 71 while heating the disk at 200° C. The substrate isobserved with an atomic force microscope, with the result that poreseach having a size of 30 nm are regularly arrayed in the resist film 72to form six rows, as shown in FIG. 7B. As shown in FIG. 7C, the glassdisk substrate 71 is etched by means of Ar ion milling to form pores 73.Finally, the pores 73 is filled with a film of a perpendicular magneticrecording material of Co—Cr—Pt followed by planarizing the surface bymeans of CMP, thereby forming recording cells 74, and subsequentlyforming a film of a diamond-like carbon on the entire surface so as toform a protective film 75, as shown in FIG. 7D.

[0151] The substrate thus prepared is observed with a magnetic forcemicroscope so as to confirm that the recording cells 74 each having asize of 30 nm are regularly arrayed within a single recording track bandso as to form six rows of the sub-tracks.

Example 9

[0152] In this Example, recording cells are formed by regularly arrayingdirectly fine particles of a magnetic material. A method ofmanufacturing a magnetic recording medium for this Example will now bedescribed with reference to FIGS. 8A to 8C.

[0153] Specifically, a colloid of fine Co—Pt particles having a size of10 nm is prepared by a known method described in S. Sun et al., Science,287 (2000) pp. 1989.

[0154] As shown in FIG. 8A, a glass disk substrate 81 is processed byelectron beam lithography so as to have a spiral groove 82 having awidth of about 110 nm defined by a convex portion having a width ofabout 150 nm and a height of about 10 nm.

[0155] Then, as shown in FIG. 8B, the colloid of the fine Co—Ptparticles is applied uniformly to the entire surface of the glass disksubstrate 81, followed by removing the solvent by evaporation andsubsequently rinsing the substrate with a pure water, thereby formingrecording cells 83 made of Co—Pt fine particles.

[0156] Further, as shown in FIG. 8C, the matrix 84 is formed bysputtering a SiO₂ film on the entire surface, followed by planarizingthe surface by means of CMP and subsequently forming a film of adiamond-like carbon so as to form the protective film 85.

[0157] The substrate thus prepared is observed with a magnetic forcemicroscope. It has been confirmed that recording cells 83 having a sizeof 10 nm are regularly arrayed within a single recording track band soas to form a hexagonal close-packed structure and to form ten rows ofthe sub-tracks.

Example 10

[0158] A method of manufacturing a magnetic recording medium for thisExample will now be described with reference to FIGS. 9A to 9D.

[0159] As shown in FIG. 9A, a groove structure is formed on a substrateas follows. Specifically, formed on a glass disk substrate 91 having adiameter of 2.5 inches are a Pd underlayer having a thickness of about30 nm and a film of a perpendicular magnetic recording material Co—Cr—Pthaving a thickness of about 50 nm so as to form a magnetic layer 92,followed by forming a SiO₂ film 93 having a thickness of about 50 nm onthe magnetic layer 92. Then, the SiO₂ film 93 is spin coated with aresist film 94. The resist film 94 thus formed is processed bynano-imprinting lithography so as to form a resist pattern such that aspiral groove having a width of about 40 nm is defined by a convexportion having a width of about 20 nm. The SiO₂ film 93 is etched toreach the magnetic layer 92 by RIE with the resist pattern thus formedused as a mask so as to transfer the groove 95 to the SiO₂ film 93.

[0160] As shown in FIG. 9B, the groove region is filled with a blockcopolymer to form a regularly arrayed structure of fine particles asfollows. Specifically, the surface of the magnetic layer 92 is subjectedto hydrophobic treatment with hexamethyldisilazane, followed by ashingthe residue of the resist pattern. On the other hand, prepared is asolution by dissolving a PS-PB block copolymer (PS having a molecularweight Mw of 5,000 and PB having a molecular weight Mw of 20,000) intoluene in a concentration of 1% W/W. The substrate is spin coated withthe solution thus prepared so as to fill the groove region transferredto the SiO₂ film 93 with the block copolymer 96. The substrate isannealed at 50° C. for 30 hours under vacuum so as to regularly arraythe block copolymer 96. As a result, formed is a structure in whichisland-like polystyrene particles 97 are surrounded by a sea-likepolybutadiene portion 98.

[0161] In the next step, recording cells are formed as follows with theregularly arrayed fine particles used as a mask. Specifically, the blockcopolymer 96 is treated with ozone so as to remove the polybutadieneportion 98, followed by washing with water. Then, the magnetic layer 92is etched by Ar ion milling with the residual polystyrene particles 97used as a mask so as to form recording cells 99.

[0162] Further, a matrix is formed in the space between the recordingcells as follows, followed by planarizing the surface, as shown in FIG.9D. Specifically, the residue of the polystyrene particles is subjectedto ashing, followed by forming a SiO₂ film having a thickness of about50 nm on the entire surface so as to fill the space between therecording cells 99 with the SiO₂ film to form the matrix 100. Thesurface of the SiO₂ film is subjected to chemical mechanical polishing(CMP) so as to planarize the surface, followed by depositing a film of adiamond-like carbon so as to form a protective film 101.

[0163]FIG. 10 schematically shows the result of observation of themagnetic recording medium thus manufactured with a magnetic forcemicroscope. As shown in FIG. 10, recording track bands 1 each having awidth of about 40 nm and isolation regions 2 each formed of a magneticlayer having a width of about 20 nm are formed alternately. Therecording cells 99 are separated from each other by the matrix 100within a single recording track band 1 so as to form a hexagonalclose-packed structure and, thus, to form a triangular lattice. Therecording cells 99 are periodically arrayed with a pitch P in the trackdirection so as to form a sub-track, and two rows of the sub-tracks 1 aand 1 b are included in a single recording track band 1. Since therecording cells 99 form a triangular lattice as described above, thenearest neighboring two recording cells 99 positioned on adjacent twosub-tracks are deviated such that the distance in the track directionbetween the center of the recording cell 99 in one sub-track and thecenter of the recording cell 99 in the adjacent sub-track is equal to ½of the pitch P of the recording cells forming the sub-track.

Example 11

[0164] A magnetic recording apparatus according to this Example will nowbe described with reference to FIGS. 11 to 14.

[0165]FIG. 11 is a perspective view showing the internal structure of amagnetic disk apparatus. As shown in the drawing, a magnetic disk 201 ismounted on a spindle motor 202 so as to be rotated in accordance withcontrol signals supplied from a control section (not shown). An actuatorarm 212 is supported on a shaft 211, and a suspension 213 and a headslider 220 at the tip of the suspension 213 are supported with theactuator arm 212. When the magnetic disk 210 is rotated, that surface ofthe head slider 220 which faces the recording medium is kept floating bya predetermined amount from the surface of the magnetic disk 201 so asto perform recording-reproducing of information. A voice coil motor 215is mounted on the proximal end of the actuator arm 212 so as to allowthe actuator arm 212 to rotate.

[0166]FIG. 12 is a cross-sectional view showing the constructions of themagnetic disk 201 and the head slider 220. The magnetic disk 201 isequal to that prepared in Example 1. As shown in the drawing, arecording layer including a recording track band in which recordingcells 28 are regularly arrayed and a protective layer 30 are formed on aglass substrate 21. Information corresponding to the address number andthe sector number of each recording track band is written in advance inthe magnetic layer forming the isolation region.

[0167] A read head 221 and a write head 222 are mounted on the tip ofthe head slider 220. A two-stage actuator (not shown) actuates the headslider 220 so as to control the positions thereof.

[0168]FIG. 13 schematically shows the planar structure of the headslider 220. The GMR read head 221 is sized at about 40 nm×about 20 nm,and the single magnetic pole write head 222 is sized at about 60nm×about 10 nm.

[0169]FIG. 14 shows the arrangement of the read head relative to therecording track band. As shown in FIG. 14, the recording cells 28 eachhaving a size of 30 nm are regularly arrayed at a predetermined pitch inthe track direction so as to form six rows of the sub-tracks in therecording track band 1. The single read head 221 reads the recordingcells on the two rows of the sub-tracks. The size of the read head 221is designed to meet the conditions given below. Specifically, the readhead 221 has a width in the track direction of 20 nm, which is smallerthan the distance between the centers of the adjacent recording cells28, and also has a length of 40 nm in the radial direction of the disk,which is larger than the distance in the radial direction between thecenters of the nearest neighboring two recording cells 28 on theadjacent two sub-tracks and is smaller than the maximum width of the tworows of the sub-tracks.

[0170] The tracking method in the magnetic recording apparatus in thisExample will now be described with reference to FIGS. 15A to 15C. Inthis Example, the position of the head slider is controlled such thatthe signals generated from the two rows of the sub-tracks formed by therecording cells regularly arrayed to form a triangular lattice areallowed to have the same intensity.

[0171]FIG. 15A shows change in the geometric positional relationshipbetween the read head and the recording cells. A detection output asshown in FIG. 15B can be obtained in accordance with the movement of theread head shown in FIG. 15A. Where the read head 221 travels along thecenterline of the two rows of sub-tracks, the frequency component f1alone, which corresponds to twice the period of the recording cells onthe sub-track, appears on the detection output (absolute value).However, if the position of the read head 221 is deviated from thecenterline, the frequency component f2 corresponding to the period ofthe recording cells on the sub-track is increased in the detectionoutput (absolute value). The phase of the frequency component f2 in thecase where the read head 221 is deviated in the direction of the firstline of the recording cells differs from that in the case where the readhead 221 is deviated in the direction of the second line of therecording cells. Therefore, it is possible to obtain a signal conformingto the change in the traveling of the read head 221, as shown in FIG.15C. It follows that, where the frequency component f2 has beendetected, it is possible to perform tracking by moving the read head 221in the radial direction in accordance with the phase thereof so as toprevent the frequency component f2 from being detected.

[0172] A method of avoiding writing in a defective region in the casewhere a defective region is included in the regular array will now bedescribed with reference to FIG. 16.

[0173] In the magnetic recording medium manufactured by utilizingself-ordering, it is possible for a disturbed region of array to beincluded in the region where the recording cells are regularly arrayed.Suppose the recording track band includes regions A and C in which therecording cells are regularly arrayed and a defective region C, in whichthe recording cell array is disturbed. As shown in FIG. 16, thedefective region C is interposed between the regions A and C.

[0174] In the magnetic recording medium for this Example, a read head ispositioned forward of a write head, and writing is controlled as followsin accordance with the signals detected by the read head. The timeinterval T at which the signals detected by the read head are expectedto appear is determined by the distance between the two adjacentrecording cells that are regularly arrayed in the track direction and bythe traveling speed of the head. The time interval T is compared withthe time interval of the signals actually generated from the read headby a controller.

[0175] While the read head is traveling over the regularly arrayedregion A, signals are regularly generated from the recording cells at asubstantially constant time interval close to the time interval T.Incidentally, if the time interval at which signals are actuallygenerated falls within the threshold value, e.g., ±30%, relative to thetime interval T, it is reasonable to judge that the recording cells areregularly arrayed. In this case, signals are supplied from thecontroller to the write head at a predetermined timing on the basis ofthe time when the read head detects signals, and writing to theregularly arrayed region A is performed by the write head.

[0176] However, when the read head travels over the defective region B,the time interval of the signals read from the recording cells isdeviated over the threshold value, e.g., ±30%, compared with the timeinterval T, and it is judged that the array of the recording cells isdisturbed. In this case, write signals from the controller to the writehead are stopped, with the result that writing to the defective region Bis not performed.

[0177] Further, if the read head comes to travel over the regularlyarrayed region C, it is judged that the recording cells are arrayedregularly. In this case, write signals are supplied from the controllerto the write head at a predetermined timing on the basis of the timewhen signals are detected by the read head, and writing to the regularlyarrayed region C by the write head is started again.

[0178] Incidentally, it is possible to set arbitrarily the criteria forthe judgment as to whether the array of the recording cells is disturbedor regularly arrayed. For example, it is possible to construct a systemsuch that it is judged that the array of the recording cells isdisturbed in the case where the disturbance in the time interval of thesignals detected by the read head is continuously generated for the timenot shorter than 3T. It is also possible to construct the system suchthat it is judged that the recording cells are arrayed regularly in thecase where the signals are detected three times consecutively by theread head at a time interval falling within the threshold value.

[0179] The tracking of the read head described above with reference toFIG. 15 and the operation to avoid writing to the defective regiondescribed above with reference to FIG. 16 are carried out by thecontroller (LSI) 225 connected to the read head 221, the write head 222and the voice coil motor as shown in FIG. 17.

Example 12

[0180] A magnetic recording apparatus for this Example will now bedescribed with reference to FIGS. 18 to 20.

[0181] Specifically, FIG. 18 is a cross-sectional view showing theconstructions of the magnetic disk and the head slider. The magneticdisk 201 is mounted on a spindle motor 202 and is rotated according tocontrol signals generated from a control section (not shown). Themagnetic disk 201 is equal to that prepared in Example 10, and comprisesa glass substrate 91, a recording layer having a recording track band 1including two rows of sub-tracks formed by recording cells 99 that arearrayed regularly, the recording layer being formed on the glasssubstrate 91, and a protective layer 101 formed on the entire surface.The recording track band 1 is magnetized in one direction over theentire region of the magnetic disk. Information corresponding to theaddress number and the sector number of each recording track band iswritten in advance in the magnetic layer forming a isolation region.

[0182] In addition to the read head 221 and the write head 222, atracking head 222 is mounted on the tip of the head slider 220. Atwo-stage actuator (not shown) actuates the head slider 220 so as tocontrol the positions thereof.

[0183]FIG. 19 schematically shows the planar construction of the headslider 220. The GMR read head 221 is sized at about 20 nm×about 15 nm,and the single magnetic pole write head 222 is circular and has a sizeof about 20 nm. Further, the GMR tracking head 223 is sized at about 40nm×about 20 nm.

[0184]FIGS. 20A and 20B show the arrangement of the read head, the writehead and the tracking head relative to the recording track band. Asshown in these drawings, the tracking head 223 is arranged over themagnetic film forming the isolation region 2 of the magnetic disk so asto read the signal generated from the isolation region 2, therebyperforming tracking so as to position the read head and the write head.In this case, the particular operation utilizes the phenomenon that thechange in signals detected by the tracking head 223 corresponds to thedeviation of the read head 221 from the sub-tracks.

Example 13

[0185] A method of manufacturing a phase change optical recording mediumfor this Example will now be described with reference to FIGS. 21A to21D.

[0186] As shown in FIG. 21A, a groove structure is formed on a substrateas follows. Specifically, formed successively on a glass disk substrate111 of 2.5 inches are a Pt reflective film 112 having a thickness ofabout 30 nm, an Al₂O₃ film 113 having a thickness of about 50 nm, whichforms a matrix, and a SiO₂ film 114 having a thickness of about 50 nm inthe order mentioned. After a resist film is formed on the SiO₂ film 114by spin coating, the resist film is processed by optical lithography soas to form a resist pattern in which a spiral groove having a width ofabout 200 nm is defined by a convex portion having a width of about 200nm. Then, the SiO₂ film 114 is etched with the resist pattern used as amask so as to transfer the groove 115 to the SiO₂ film 114.

[0187] As shown in FIG. 21B, the groove region is filled with a blockcopolymer to form a regular array structure of fine particles asfollows. Specifically, prepared is a solution by dissolving apolystyrene-polymethyl methacrylate block copolymer (PS having amolecular weight Mw of 80,000 and PMMA having a molecular weight Mw of20,000) in toluene in a concentration of 1% w/w. Then, The substrate isspin coated with the solution thus prepared so as to fill the grooveregion transferred to the SiO₂ film 114 with the block copolymer 116.Further, the substrate is annealed at 150° C. for 30 hours under vacuumso as to regularly array the block copolymer 116. As a result, formed isa structure in which island-like PMMA particles 117 are surrounded by asea-like PS portion 118.

[0188] As shown in FIG. 21C, a pore structure for the recording cells isformed as follows. Specifically, the block copolymer 116 is treated withultraviolet light, followed by washing with water. Then, a Cr layer 119is formed by oblique vapor deposition. After formation of the Cr layer119, holes extending to reach the Al₂O₃ layer 113 are formed by RIE,followed by transferring holes 120 to the Al₂O₃ layer by Ar ion millingso as to form a matrix consisting of the Al₂O₃ film 113.

[0189] Further, as shown in FIG. 21D, recording cells are formed and thesurface thereof is planarized as follows. Specifically, a film of aphase change material In—Sb—Te is deposited in a thickness of about 30nm so as to fill the holes 120, thereby forming the recording cells 121.Further, the surface is subjected to CMP, followed by forming a SiO₂film on the entire surface so as to form the protective film 122.

[0190]FIG. 22 schematically shows the result of observation of the phasechange optical recording medium thus manufactured with a near-fieldoptical microscope. As shown in FIG. 22, recording track bands 1 eachhaving a width of about 200 nm and isolation regions 2 made of Al₂O₃film 113 having a width of about 200 nm are formed alternately. Therecording cells 121 form a hexagonal close-packed structure within asingle recording track band 1 and, thus, form a triangular lattice. Therecording cells 199 are periodically arrayed with a pitch P in the trackdirection so as to form a sub-track, and six rows of the sub-tracks 1 ato 1 f are included in the recording track band 1. The nearestneighboring two recording cells 121 positioned on adjacent twosub-tracks are deviated such that the distance in the track directionbetween the center of the recording cell 121 in one sub-track and thecenter of the recording cell 121 in the adjacent sub-track is equal to ½of the pitch P of the recording cells forming the sub-track.

Example 14

[0191] A phase change optical recording apparatus for this Example willnow be described with reference to FIGS. 23 and 24.

[0192] Specifically, FIG. 23 is a cross-sectional view showing theconstructions of a phase change optical disk 301 and the head slider. Asshown in the drawing, the optical disk 301 is mounted on a spindle motor302 and is rotated according to control signals supplied from a controlsection (not shown). The optical disk 301 is equal to that prepared inExample 13, and comprises a glass substrate 111, a recording layerhaving a recording track band in which the recording cells 121 areregularly arrayed, the recording layer being formed on the glasssubstrate 111, and a protective layer 122 formed on the entire surface.

[0193] A laser resonance type optical detection read head 311 and aplanar oscillation type laser write head 312 are mounted on tip of thehead slider 310. A two-stage actuator (not shown) actuates the headslider 310 so as to control the positions thereof.

[0194]FIG. 24 schematically shows the planar construction of microapertures formed in the front surface of each head of the head slider310. The micro aperture of the read head 311 is sized at about 40nm×about 20 nm, and the micro aperture of the write head 312 is sized atabout 60 nm×about 10 nm.

[0195] It is possible to perform tracking of the read head and operationto avoid writing to a defective region in this Example by the methodsimilar to that for Example 11.

Example 15

[0196] A magnetic recording apparatus for this Example will now bedescribed with reference to FIGS. 25 to 27. Specifically, FIG. 25 is across-sectional view showing the constructions of the magnetic disk 201and the head slider 220. FIG. 26 schematically shows the planarconstruction of the head slider 220. Further, FIG. 27 shows thearrangement of read head, the write head and the tracking head relativeto the recording track band.

[0197] As shown in FIG. 25, the magnetic disk 201 is mounted on aspindle motor 202 and is rotated according to control signals suppliedfrom a control section (not shown). The magnetic disk 201 is equal tothat prepared in Example 5, and comprises a glass substrate 41, arecording layer formed on the glass substrate 41, and a protective layer51 formed on the entire surface. The recording layer noted abovecomprises a recording track band 1 including six rows of sub-tracksformed of recording cells 50 that are arrayed regularly.

[0198] Read heads 231, a tracking head 232 and write heads 233 aremounted on the tip of the head slider 220. A two-stage actuator (notshown) actuates the head slider 220 so as to control the positionsthereof.

[0199] As shown in FIG. 26, used in this Example is a multi-channel headincluding five GMR read heads 231 arranged in a manner to correspond tothe five rows of the sub-tracks and each sized at about 20 nm×about 15nm, a GMR tracking head 232 sized at 20 nm×about 15 nm and arranged tocorrespond to the sixth line of the sub-track, and five circular singlemagnetic pole write heads 233 each having a size of 20 nm arranged tocorrespond to the five rows of the sub-tracks like the read heads 231.

[0200] As shown in FIG. 27, tracking signals are detected in thisExample by the tracking head 232 from the recording cells on the sixthsub-track that is positioned at the edge of the recording track band 1so as to position of the read heads and the write heads. In thisExample, it is possible to confirm instantly write signals by the readheads 231.

Example 16

[0201] A magnetic recording medium for this Example will now bedescribed with reference to FIGS. 28 to 30. FIG. 28 is a cross-sectionalview showing the constructions of the magnetic disk and the head slider.FIG. 29 schematically shows the planar construction of the head slider.Further, FIG. 30 shows the arrangement of the read head, the write headand the tracking head relative to the recording track band.

[0202] As shown in FIG. 28, the magnetic disk 201 is mounted on thespindle motor 202 and is rotated according to control signals generatedfrom a control section (not shown). The magnetic disk 201 is prepared bynano-imprinting using a master disk manufactured as in Example 8. Asshown in FIG. 30, rectangular recording cells 150 each sized at 30 nm×15nm are regularly arrayed within the recording track band 1 to form threerows of sub-tracks on the magnetic disk 201. The recording cells 150 arearrayed at a pitch P in the track direction to form a sub-track. Itshould be noted that the nearest neighboring two recording cells 150positioned on adjacent two sub-tracks are deviated by a distance equalto ⅓ of the pitch P noted above.

[0203] A read head 241 and a write head 242 are mounted on the tip ofthe head slider 220. A two-stage actuator (not shown) actuates the headslider 220 so as to control the positions thereof.

[0204] As shown in FIG. 29, the read head 241 is sized at about 90nm×about 15 nm, and the write head 242 is sized at about 110 nm×about 15nm.

[0205] As shown in FIG. 30, the single read head 241 reads the recordingcells 150 on three rows of sub-tracks regularly arrayed at apredetermined pitch within the recording track band 1. The size of theread head 241 noted above is designed to meet the conditions givenbelow. Specifically, the read head 241 has a width in the trackdirection of 15 nm, which is smaller than the distance in the trackdirection between the centers of the nearest neighboring recording cellson adjacent two sub-tracks, and has a length of 90 nm in the radialdirection of the disk, which is larger than the distance in the radialdirection between the centers of the nearest neighboring two recordingcells on adjacent two sub-tracks and smaller than the maximum width ofthe three rows of the sub-tracks.

[0206] In this Example, it is possible to perform tracking bycontrolling the position of the head slider such that the signalsgenerated from two of the three rows of sub-tracks are allowed to havethe same intensity.

Example 17

[0207] A method of manufacturing a charge-storing recording medium forthis Example will now be described with reference to FIGS. 31A to 31D.

[0208] As shown in FIG. 31A, a groove structure is formed on a substrateas follows. Specifically, formed successively on a glass disk substrate131 of 2.5 inches are an Au underlying electrode 132 having a thicknessof about 30 nm, an Al₂O₃ film 133 having a thickness of about 50 nm,which forms a matrix and an isolation region, and a SiO₂ film 134 havinga thickness of about 50 nm in the order mentioned. After a resist filmis formed on the SiO₂ film 134 by spin coating, the resist film isprocessed by optical lithography so as to form a resist pattern in whicha spiral groove having a width of about 200 nm is defined by a convexportion having a width of about 200 nm. Then, the SiO₂ film 134 isetched with the resist pattern used as a mask so as to transfer thegroove 135 to the SiO₂ film 134.

[0209] As shown in FIG. 31B, the groove region is filled with a blockcopolymer to form a regular array structure of fine particles asfollows. Specifically, prepared is a solution by dissolving apolystyrene-polymethyl methacrylate block copolymer (PS having amolecular weight Mw of 80,000 and PMMA having a molecular weight Mw of20,000) in toluene in a concentration of 1% w/w. Then, the substrate isspin coated with the solution thus prepared so as to fill the grooveregion transferred to the SiO₂ film 134 with the block copolymer 136.Further, the substrate is annealed at 150° C. for 30 hours under vacuumso as to regularly array the block copolymer 136. As a result, formed isa structure in which island-like PMMA particles 137 are surrounded by asea-like PS portion 138.

[0210] As shown in FIG. 31C, a pore structure for the recording cells isformed as follows. Specifically, the block copolymer 136 is treated withultraviolet light, followed by washing with water. Then, a Cr layer 139is formed by oblique vapor deposition. After formation of the Cr layer139, holes extending to reach the Al₂O₃ layer 133 are formed by RIE,followed by transferring holes 140 having a depth of about 10 nm to theAl₂O₃ layer by Ar ion milling so as to form a matrix consisting of theAl₂O₃ film 133.

[0211] Further, as shown in FIG. 31D, recording cells are formed and thesurface thereof is planarized as follows. Specifically, an Au film as acharge-storing material is deposited in a thickness of about 10 nm so asto fill the holes 140, thereby forming the recording cells 141. Further,the surface is subjected to CMP, followed by forming a SiO₂ film on theentire surface so as to form the protective film 142.

[0212] A charge-storing recording apparatus for this Example will now bedescribed with reference to FIGS. 32 and 33. FIG. 32 is across-sectional view showing the constructions of the recording disk ofcharge-storing medium and the head slider. As shown in the drawing, therecording disk 401 is mounted on a spindle motor 402 and is rotatedaccording to control signals supplied from a control section (notshown). The underlying electrode 132 is electrically contacted tooutside making it possible to apply a voltage to the underlyingelectrode 132. A SET sensor 411 as a read head and a Ti electrode 412whose end is sharpened to about 10 nmφ as a write head are mounted ontip of the head slider 410. A pulsed minus voltage is applied to the Tielectrode 412 so as to emit electrons to the recording cells 141 ascharge-storing areas, thereby performing writing.

[0213]FIG. 33 schematically shows the planar construction of the headslider 410. The SET sensor 411 and the Ti electrode 412 are mounted ontip of the head slider.

[0214] It is possible to perform tracking of the read head and operationto avoid writing to a defective region in this Example by the methodsimilar to that for Example 11.

[0215] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the present invention in itsbroader aspects is not limited to the specific details andrepresentative embodiments shown and described herein. Accordingly,various modifications may be made without departing from the spirit orscope of the general inventive concept as defined by the appended claimsand their equivalents.

What is claimed is:
 1. A recording medium, comprising: a substrate; anda recording layer formed on the substrate comprising (a) a recordingtrack band, and (b) recording cells regularly arrayed in the recordingtrack band to form a plurality rows of sub-tracks, wherein the recordingcells included in each sub-track are formed apart from each other at apitch P in the track direction, and wherein nearest neighboring tworecording cells, each positioned on adjacent two sub-tracks in the trackband, are formed apart from each other at a pitch P/n in the trackdirection, where 2≦n≦5.
 2. The recording medium according to claim 1,wherein the medium has a disk shape, and wherein the track direction isthe circumference direction.
 3. The recording medium according to claim1, wherein recording track bands and isolation regions are alternatelyarranged in the track width direction.
 4. The recording medium accordingto claim 1, wherein the recording cells are formed of a magneticrecording material.
 5. The recording medium according to claim 1,wherein the recording cells are formed of an optical recording material.6. The recording medium according to claim 1, wherein the recordingcells are formed of a charge accumulating material.
 7. The recordingmedium according to claim 1, wherein the recording cells are isolated bya non-recording material in the recording track band.
 8. The recordingmedium according to claim 3, wherein the isolation regions are formed ofa non-recording material.
 9. The recording medium according to claim 3,wherein the isolation regions are formed of a recording material equalto the material of the recording cells.
 10. The recording mediumaccording to claim 1, wherein the recording cells form a hexagonalclose-packed structure.
 11. The recording medium according to claim 1,wherein the recording cell has a size of 2 to 100 nm, and the pitch Pbetween the recording cells is 2 to 100 nm.
 12. A method ofmanufacturing a recording medium, comprising: forming on a substrate acontinuous or intermittent groove region, or a band region containing aspecified chemical component, which corresponds to a recording trackband; forming a two-dimensional regular array structure of self-orderingmolecules or fine particles in the groove region or the band region; andforming recording cells corresponding to the regular array structure.13. The method according to claim 12, wherein the continuous orintermittent groove region or the band region containing a specifiedchemical component, which corresponds to the recording track band, isformed on the substrate by optical lithography, electron beamlithography or nano-imprinting lithography
 14. A recording apparatus,comprising: a recording medium comprising a substrate and a recordinglayer formed on the substrate comprising (a) a recording track band and(b) recording cells regularly arrayed in the recording track band toform a plurality rows of sub-tracks, wherein the recording cellsincluded in each sub-track are formed apart from each other at a pitch Pin the track direction, and wherein nearest neighboring two recordingcells, each positioned on adjacent two sub-tracks in the track band, areformed apart from each other at a pitch P/n in the track direction,where 2≦n≦5; a write head; and a read head.
 15. The recording apparatusaccording to claim 14, wherein the read head is formed to read signalsfrom the recording cells positioned on the plural sub-tracks, andwherein a controller controlling tracking of the read head on the basisof the signals produced from the recording cells positioned on theplural sub-tracks is further provided.
 16. The recording apparatusaccording to claim 15, wherein the read head has a width large enough toread signals from the recording cells positioned on two to n rows of thesub-tracks.
 17. The recording apparatus according to claim 14, whereinthe shape of the write head is substantially similar to the shape of therecording cell.
 18. A recording apparatus writing to and reading from arecording medium comprising a substrate and a recording layer formed onthe substrate comprising (a) a recording track band and (b) recordingcells regularly arrayed in the recording track band to form a pluralityrows of sub-tracks, wherein the recording cells included in eachsub-track are formed apart from each other at a pitch P in the trackdirection, and wherein nearest neighboring two recording cells, eachpositioned on adjacent two sub-tracks in the track band, are formedapart from each other at a pitch P/n in the track direction, where2≦n≦5, comprising: a write head; a read head; and a controllercontrolling write timing signals supplied to the write head inaccordance with signals generated from the read head.
 19. The apparatusaccording to claim 18, wherein the controller controls the write timingsignals supplied to the write head by comparing (a) a time intervaldetermined by the pitch of the recording cells regularly arrayed in thetrack direction and a traveling speed of the read head with (b) a timeinterval of signals generated from the read head.
 20. The recordingapparatus according to claim 18, wherein the read head has a width largeenough to read signals from the recording cells positioned on two to nrows of the sub-tracks.
 21. The recording apparatus according to claim18, wherein the shape of the write head is substantially similar to theshape of the recording cell.
 22. The recording apparatus according toclaim 18, further comprising a second read head for tracking.
 23. Therecording apparatus according to claim 18, further comprising a sourceof an electron beam or near-field light assisting the write head.